Generally, there are two methods for cutting a steel plate into various shapes: one in which cutting is started from an end of the steel plate, and one in which cutting is started from a desired position in the steel plate surface. The latter is a piercing start method in which a through hole is formed in the steel plate at a predetermined position, and in which cutting is started from this through hole (which operation will hereinafter be referred to as "piercing start"). By piercing start, a desired shape in the steel plate surface can be cut out, and plasma cutting is, of course, based on the above two methods.
In the case of cutting a steel plate with a plasma cutting machine by effecting a piercing start, the cut material melted by the plasma torch is blown onto a hole edge portion, attaches to the same, and is further accumulated as a dross. This dross may interfere with the extreme end of the plasma torch to damage the same when the plasma torch is moved, or the melt blown and raised may be attached to the extreme end of the plasma torch so that the plasma jetting is obstructed or that a double arc is caused, resulting in a reduction in cutting quality. Conventionally, therefore, piercing is performed while the plasma torch is being held in a position such as to be free from the influence of the dross, and cutting is thereafter performed by gradually moving the plasma torch downward to a predetermined position. In this method, however, chips formed by cutting the steel plate are increased. For this reason, a method of previously applying an anti-dross-attachment agent to a piercing start portion of the steel plate has recently been studied.
Ordinarily, an anti-dross-attachment agent is a liquid having very small graphite grains as a main component. Such an anti-dross-attachment agent is applied by a method of manually applying or spraying the anti-dross-attachment agent, a method of mounting an anti-dross-attachment agent application apparatus on the plasma cutting machine, or other methods. In the case of manual application of an anti-dross-attachment agent, however, it is difficult to uniformly apply the agent, and the application operation is obstructive to the promotion of unmanning or automatization of the plasma cutting operation. In addition, there is no anti-dross-attachment agent application apparatus satisfactory in terms of unmanning or automatizing the plasma cutting operation.
In view of the above-described problems of the conventional methods or apparatus, an object of the present invention is to provide an anti-dross-attachment agent application apparatus for plasma cutting satisfactory in terms of unmanning or automatizing the plasma cutting operation.